A Strategic NH3-Dosing Approach for the Minimization of N2O Production During NH3-SCR Reactions over Cu-SSZ-13 Catalysts

The undesired production of N2O during NH3-SCR reactions is investigated over a reference commercial Cu-CHA catalyst. Steady-state experiments performed in the 150–500 °C temperature range exhibit a bimodal trend in the N2O formation profile, confirming the existence of two different reaction mechanisms occurring at low and high temperatures. Focusing on a low-to-medium T-range, N2O production, usually ascribed to NH4NO3 formation and decomposition, increases with the NO2/NOx ratio. However, an excess of NO2 leads to a decrease in the N2O release due to ammonium nitrate deposition and catalyst clogging phenomena. Steady-state and dynamics experiments show the promoting effect of both NH3 feed concentration and NH3 storage on N2O production at T > 200 °C. Surprisingly, N2O decreases with increasing NH3/NOx ratio at lower temperature. A novel approach based on the strategic injection of NH3 is also applied to mitigate the N2O formation while maintaining high deNOx activity. Remarkably, complete NOx conversion and 11